Department

Description

Process Steps: 1. Either: a) a Portable Document Format (PDF) version of the map provided the Bureau of Economic Geology, University of Texas at Austin was converted from pdf to Tagged Image File Format (TIFF) or b) a paper map was scanned and saved in TIFF at 200 dots per inch (dpi) and the original map size. The TIFF file was then opened in Adobe Photoshop, converted from RGB or other multiband mode to Indexed Color or Grayscale, rotated so that the top map neat line was horizontal, set to 200 dpi, and clipped to the neat lines, removing the map collar. A version with the map collar was retained. 2. Using tools within ArcGIS 10.2, both the collared and collarless Indexed Color TIF images were then either: a) georeferenced to Universal Transverse Mercator (UTM) zone 14, North American Datum 1927 (NAD27) coordinates using a digital 1:24,000 U.S. Geological Survey quadrangle index map from the Texas Natural Resources Information Services as the referencing layer or b) georeferenced to World Geodetic System 1984 (WGS84) geographic coordinates using the map corner coordinates for reference. Keyhole Markup Language (KML, KMZ) and GeoPDF map versions were created from these georeferenced maps by tools and export options in ArcGIS.
Up to five different georeferenced versions of the original map and, when available, the map pamphlet, are available for download. The versions, as distinguished by Download File name, are: 1) Mapname.pdf: a GeoPDF of the collarless map referenced to UTM zone 14 coordinates relative to the NAD27 datum. The acronym "GAT" (Geologic Atlas of Texas) indicates the source and a map original available only at a small scale (1:250,000). 2) Mapname.kmz: a KML version of the collarless map for viewing in Google Earth. The spatial reference is geographic coordinates relative to the WGS84 datum. 3) Mapname_GCSWGS84_collarless.zip: zipped files that include a collarless map in TIFF format and ancillary ArcGIS v. 10.2 georeferencing files and metadata. The spatial reference is geographic coordinates relative to the WGS84 datum. 4) Mapname_UTM_collarless.zip: a zipped file that includes a collarless map in TIFF format and ancillary ArcGIS v. 10.2 georeferencing files and metadata. The spatial reference is UTM zone 14 coordinates relative to the NAD27 datum. 5) Mapname_with_collar.zip: the same as above but with the map collar still intact. 6) Mapname_pamphlet.pdf: a copy of the map pamphlet in PDF format.
Any file name beginning with "GAT" indicates a map that was clipped from the Geologic Atlas of Texas (scale 1:250,000), the only published source for that area, and thus a much smaller-scale map than all other quadrangles.
Further metadata for each map version are available in Federal Geographic Data Committee (FGDC)-compliant metadata file within the zip files, or in the document properties of the GeoPDF and KML files when opened in Adobe Acrobat or Google Earth."For use by Barton Spring Edwards Aquifer Conservation District (BSEACD) Central Texas geologic mapping project"